Rotary/push buttons have a slide bearing and centrally disposed push button activation or a ball bearing having a non-centrally placed push button activation with or without additional gearings.
Since slide bearings require clearance between the guide surfaces, this solution generally causes a wobbling of the rotary button. In the second solution with the ball bearing, the activation of the push button is not centrally placed, which generates a higher frictional torque. For effective feedback and tactile response, minimal friction and a minimal, wobbling of the rotary button, are removed. However, both properties (minimal friction and a minimal wobbling) work in opposition to one another. These two properties are described below:                minimal guide clearance=>minimal wobbling of the rotary button, high friction        large guide clearance=>minimal friction, greater wobbling of the rotary button.        
A compromise between these two properties may be pursued. However, the smaller the diameter of the rotary-push button controller and of the resulting installation space, may make it more difficult to minimize the wobbling of the rotary button.
A switch device has a coaxial assembly along the longitudinal axis of a cylindrical core, which extends axially from a core base to a distal end. The core base is fixed to a base plate. An outer knob extends from the knob base to a distal knob top, the knob being rotatable along the longitudinal axis about the cylindrical core. A switching generates an electrical signal dependent on the rotations of the knob. A guiding of the knob in its movement relative to the cylindrical core is also provided. This knob guiding includes an upper-guide in the vicinity of the distal end of the cylindrical core and of the knob-top, as well as a lower-guide in the vicinity of the core base and the knob base. In this configuration, the upper-guide, in turn, includes rolling elements, these rolling elements roll between an inner race of the upper-guide, which is an integral component of the core, and an outer race of the upper-guide, which is an integral component of the knob. With the upper ball bearing arrangement thus provided, friction that occurs as a result of the rotational movement of the knob is prevented.
A rotary control/push-control device for a human-machine interface, in particular, for a vehicle component, such as an air conditioner is known. This rotary control/push-control device includes a rotary/push element, which is rotatable about a guide shaft and axially movable along the guide axis. The rotary/push-control device also includes a roller bearing unit having an outer bearing ring, an inner bearing ring and rollers disposed between outer bearing ring and inner bearing ring. In this configuration, the outer bearing ring—or alternatively, the inner bearing ring—is connected to the rotary/push element and is simultaneously rotatable by the latter. A rotation sensor detects the rotational movement of the rotary/push element. The rotary control/push control device also includes at least one of the two following groups of features, namely, a pressure sensor that responds to an axial movement of the rotary control/push control device along the guide shaft from a starting position to a depressed position, and a return element for automatically moving the rotary/push element to its starting position. The return element in this case acts directly or indirectly on the roller bearing unit. The inner bearing ring—or alternatively, the outer bearing ring—is guided on the guide axis in an axially movable manner and secured on said axis to prevent the bearing ring from rotating.